The Defense Ministry said Tuesday a second group of five Sukhoi aircraft had arrived in the country, implicitly as part of the Russian deal.

But the London-based International Institute for Strategic Studies (IISS) said its analysts believed the jets came from Iran.

IISS said Iranian Su-25s were given “a narrow range of six-digit serial numbers” and that the two digits painted on the three planes shown in the video correspond to the final digits of Iranian serial numbers.

IISS also posted side-by-side photos of one of the aircraft in the video and an Iranian Su-25, showing that the numbers and camouflage pattern are the same.

“Attempts to conceal original operator markings are also apparent, with evidence of key positions being painted over,” the think tank said, according to AFP.

Additionally, the three aircraft carried wing-mounted fuel tanks, indicating that they were flown in, while the first group of aircraft delivered under the Russian deal arrived disassembled in a cargo plane.